Soldering apparatus for soldering circuit boards has been proposed in the past which minimizes oxidation of the solder and dross production by controlling the atmosphere in the area of the soldering operation. Typical of such apparatus is that shown in U.S. Pat. No. 4,921,156 to E. Hohnerlein which provides a long entrance and exit tunnel to the soldering chamber. Molten solder is provided to the soldering chamber through a supply channel from a tub of molten solder. The soldering chamber is sealed off from the ambient atmosphere by a skirt which dips down into the tub of solder.
While this arrangement controls the atmosphere in the location of the soldering process, the molten solder in the tub and the pumps which are required for the process, are both exposed to normal atmosphere. As a result, oxidation of the solder occurs and dross is formed which interferes both with the soldering process and the operation of the pumps and the pump bearings.